Toward High-Voltage Lithium–Metal Batteries with Aliphatic Dinitrile Additives: A Multiscale Theoretical Study

Developing electrolytes compatible with high-voltage operation is critical for high-energy-density lithium metal batteries. Aliphatic dinitriles, owing to the ability of cyano groups to stabilize cathode interfaces and suppress transition metal dissolution, are promising high-voltage electrolyte additives; however, structure–property relationships remain insufficiently understood. Here, adiponitrile was used as the parent molecule, and 18 derivatives were designed by varying backbone length and alkyl branching. Quantum chemical calculations show that structural modification tunes the electrochemical stability window, with oxidation potentials further reduced upon interaction with PF6–. Binding energy analysis confirms strong coordination with both Li+ and PF6–, while molecular dynamics simulations reveal pronounced changes in Li+ solvation structure and transport behavior. Mechanistic verification reveals that the additive does not generate harmful HF during oxidation and can efficiently suppress the hydrolysis of PF5. Selected candidates preferentially form anion-coordinated solvation complexes that undergo oxidative decomposition at the cathode, which is suggested to contribute to the formation of dense, inorganic-rich cathode electrolyte interphases (CEI). These additives may also participate in forming a stable solid electrolyte interphase (SEI), contributing to improved interfacial stability on both electrodes. This work establishes structure–property relationships and offers a multiscale coupling framework for the rational design of electrolyte additives.